Gin-san takes history lessons, and teaches you how to hide your porn mags?
Tsukuyo tries to teach Seita history, the subject he's not great at. However, her training (?) methods end up leaving him scarred, which makes desperate Seita ask Gin-san to take over as his tutor...
Or is it so you can use the 
"I'm just randomly putting books
أو فعلتَ هذا لتوفير تبرير "أنا أضعهم أينما توفّرت المساحة الشاغرة وحسب
¿Dices que solo las pusiste donde pudiste
 y que no las estabas ocultando?
É para poder dizer que 
está só guardando os livros